1. Field of the Invention
The present invention relates in general to the field of power conversion, and more particularly to a system and method for managing negative voltage in a power supply overvoltage failure event.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems typically include a number of electronic components that are sensitive to alterations in the voltage supplied for the components to operate. Excessive positive or negative voltage surge events can cause catastrophic failure to the components. To provide appropriately regulated DC-DC voltage conversion for sensitive components, information handling systems typically have a number of synchronous Buck regulators. For instance, a typical portable information handling system will have at least seven such synchronous regulators providing different level voltage to components such as the CPU, ICH, DDR and hard disk driver. Synchronous Buck regulators control voltage with a control MOSFET, a synchronous MOSFET and an LC tank circuit under a regulator controller. For instance, in an overvoltage event, regardless of the overvoltage condition that induced the overvoltage event, the regulator controller turns on the synchronous MOSFET to rapidly discharge an output capacitor of the LC tank circuit and reduce the output voltage. Synchronous Buck regulators thus protect information handling systems from overvoltage events that occur as a result of any number of fault conditions, such as a short, changes in reference voltage, component aging or feedback loop disconnect.
One difficulty with synchronous Buck regulators is that, in some situations, the correction to an overvoltage event provided by the capacitor of the tank circuit results in a negative voltage output. For instance, when energy is already stored in the LC tank circuit, a low resistance exists in the synchronous MOSFET and/or the load on the regulator is relatively low, a relatively quick response of a negative voltage of 2 Volts or less may be reached. A negative voltage event can present as much destructive risk to hardware components as an overvoltage event and is not guarded against in a conventional synchronous Buck regulator. One solution to the risk of a negative voltage from a synchronous Buck regulator is to connect a power schottky diode across the output of the regulator to act as a reverse-polarity clamp. However, the use of a diode adds to the cost of an information handling system and takes up a considerable amount of printed circuit board area, such as on a motherboard. The use of the diode also adds to manufacturing cost and difficulty by adding another component to the manufacture process.